Cooperating for Peace and Security is a comprehensive survey of multilateral security cooperation since 1989. With essays by leading experts on topics from peacekeeping to nuclear security, it goes beyond theoretical discussions of the value of cooperation to show how the operational activities of international organizations meet the security needs of states. In particular, it explores the complex relationship between multilateralism and American security concerns. Covering the UN, NATO, and regional organizations, the authors show that U.S. interests have often shaped institutions. But, more strikingly, other states have also driven institutional change without U.S. support or even in the face of American opposition. This raises important questions about how the balance of power shapes international institutions. In a period of shifting power dynamics, the empirical evidence on security cooperation gathered in this volume is a unique resource for scholars and policy-makers concerned with the future of international institutions.